title: Genetic and functional properties of uncultivated MCG archaea assessed by metagenome and gene expression analyses.
abstract: The Miscellaneous Crenarchaeota group (MCG) Archaea is one of the predominant archaeal groups in anoxic environments and may have significant roles in the global biogeochemical cycles. However, no isolate of MCG has been cultivated or characterized to date. In this study, we investigated the genetic organization, ecophysiological properties and evolutionary relationships of MCG archaea with other archaeal members using metagenome information and the result of gene expression experiments. A comparison of the gene organizations and similarities around the 16S rRNA genes from all available MCG fosmid and cosmid clones revealed no significant synteny among genomic fragments, demonstrating that there are large genetic variations within members of the MCG. Phylogenetic analyses of large-subunit+small-subunit rRNA, concatenated ribosomal protein genes and topoisomerases IB gene (TopoIB) all demonstrate that MCG constituted a sister lineage to the newly proposed archaeal phylum Aigarchaeota and Thaumarchaeota. Genes involved in protocatechuate degradation and chemotaxis were found in a MCG fosmid 75G8 genome fragment, suggesting that this MCG member may have a role in the degradation of aromatic compounds. Moreover, the expression of a putative 4-carboxymuconolactone decarboxylase was observed when the sediment was supplemented with protocatechuate, further supporting the hypothesis that this MCG member degrades aromatic compounds.
authors.affiliation: State Key Laboratory of Microbial Metabolism and State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China.|3Present Address: Department of Marine Science, University of Georgia, Athens, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Meng
authors.affiliation: State Key Laboratory of Microbial Metabolism and State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
authors.forename: Jun
authors.initials: J
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Microbial Metabolism and State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
authors.forename: Dan
authors.initials: D
authors.lastname: Qin
authors.affiliation: State Key Laboratory of Microbial Metabolism and State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
authors.forename: Ying
authors.initials: Y
authors.lastname: He
authors.affiliation: State Key Laboratory of Microbial Metabolism and State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Xiao
authors.affiliation: State Key Laboratory of Microbial Metabolism and State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China. fengpingw@sjtu.edu.cn.|Key Laboratory of Systems Biomedicine, Ministry of Education, Shanghai Jiao Tong University, Shanghai, People's Republic of China. fengpingw@sjtu.edu.cn.
authors.forename: Fengping
authors.initials: F
authors.lastname: Wang
mesh_terms: D001105:Archaea / Q000145:classification* / Q000235:genetics* / Q000378:metabolism; D002262:Carboxy-Lyases / Q000378:metabolism; D004264:DNA Topoisomerases, Type I / Q000235:genetics; D063366:Estuaries; D019015:Geologic Sediments / Q000382:microbiology*; D054892:Metagenome; D008969:Molecular Sequence Data; D010802:Phylogeny; D019642:RNA, Archaeal / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics / Q000378:metabolism; D012269:Ribosomal Proteins / Q000235:genetics
chemical_list: D019642:RNA, Archaeal; D012336:RNA, Ribosomal, 16S; D012269:Ribosomal Proteins; D002262:Carboxy-Lyases; C019832:4-carboxymuconolactone decarboxylase; D004264:DNA Topoisomerases, Type I